package sdk.webview.fmc.com.fmcsdk.util;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Created by chenqi on 2018/9/28.
 * 描述：
 */

public class Base64 {
  private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();

  public static String encode(byte[] data) {
    int start = 0;
    int len = data.length;
    StringBuffer buf = new StringBuffer(data.length * 3 / 2);

    int end = len - 3;
    int i = start;
    int n = 0;

    while (i <= end) {
      int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 0x0ff) << 8) | (((int) data[i + 2]) & 0x0ff);

      buf.append(legalChars[(d >> 18) & 63]);
      buf.append(legalChars[(d >> 12) & 63]);
      buf.append(legalChars[(d >> 6) & 63]);
      buf.append(legalChars[d & 63]);

      i += 3;

      if (n++ >= 14) {
        n = 0;
        buf.append(" ");
      }
    }

    if (i == start + len - 2) {
      int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 255) << 8);

      buf.append(legalChars[(d >> 18) & 63]);
      buf.append(legalChars[(d >> 12) & 63]);
      buf.append(legalChars[(d >> 6) & 63]);
      buf.append("=");
    } else if (i == start + len - 1) {
      int d = (((int) data[i]) & 0x0ff) << 16;

      buf.append(legalChars[(d >> 18) & 63]);
      buf.append(legalChars[(d >> 12) & 63]);
      buf.append("==");
    }

    return buf.toString();
  }

  private static int decode(char c) {
    if (c >= 'A' && c <= 'Z')
      return ((int) c) - 65;
    else if (c >= 'a' && c <= 'z')
      return ((int) c) - 97 + 26;
    else if (c >= '0' && c <= '9')
      return ((int) c) - 48 + 26 + 26;
    else
      switch (c) {
        case '+':
          return 62;
        case '/':
          return 63;
        case '=':
          return 0;
        default:
          throw new RuntimeException("unexpected code: " + c);
      }
  }

  /**
   * Decodes the given Base64 encoded String to a new byte array. The byte array holding the decoded data is returned.
   */

  public static byte[] decode(String s) {

    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    try {
      decode(s, bos);
    } catch (IOException e) {
      throw new RuntimeException();
    }
    byte[] decodedBytes = bos.toByteArray();
    try {
      bos.close();
      bos = null;
    } catch (IOException ex) {
      System.err.println("Error while decoding BASE64: " + ex.toString());
    }
    return decodedBytes;
  }

  private static void decode(String s, OutputStream os) throws IOException {
    int i = 0;

    int len = s.length();

    while (true) {
      while (i < len && s.charAt(i) <= ' ')
        i++;

      if (i == len)
        break;

      int tri = (decode(s.charAt(i)) << 18) + (decode(s.charAt(i + 1)) << 12) + (decode(s.charAt(i + 2)) << 6) + (decode(s.charAt(i + 3)));

      os.write((tri >> 16) & 255);
      if (s.charAt(i + 2) == '=')
        break;
      os.write((tri >> 8) & 255);
      if (s.charAt(i + 3) == '=')
        break;
      os.write(tri & 255);

      i += 4;
    }
  }
}
